Project Summary/Abstract The goal of this project is to improve risk-stratification for patients who present to the emergency department (ED) with syncope (transient loss of consciousness), in order to better delineate which patients require admission and which can be safely discharged home. Syncope and pre-syncope (the sensation of impending loss of consciousness) are common reasons to present to the ED, representing over 1.3 million visits per year in the United States. Although syncope is most often benign, it can occasionally be caused by serious cardiopulmonary diseases such as cardiac arrhythmia, acute coronary syndrome, or pulmonary embolism. Despite thorough evaluation in the ED, the cause of syncope remains unknown in over 50% of cases, which leads to a large number of syncope patients being admitted for observation and/or further testing. These admissions to the hospital or observation unit are low-yield, costly, and expose patients to the possibility of iatrogenic harm. In response to this, two groups of researchers have developed distinct syncope risk-stratification tools: the US Syncope Risk Score and the Canadian Syncope Risk Score. These scores use a combination of clinical, electrocardiographic, and laboratory variables to predict the risk of serious clinical outcomes at 30 days. While promising, these two risk scores require external validation prior to widespread clinical implementation. In Aim 1 of this proposal, we will prospectively collect data on ~1,370 ED patients with syncope/pre-syncope and follow them for 30 days to validate the predictive accuracy of these two risk scores. In Aim 2, we will assess the impact of implementing these scores by measuring their potential effect on healthcare utilization and costs. Existing care will be used as the reference strategy and will be compared with a simple risk-based clinical algorithm: Direct discharge for low risk patients (under 2% risk of serious outcome at 30 days), and hospitalization for medium- and high-risk patients. If validated and shown to safely reduce healthcare utilization, these syncope risk scores could play a major role in improving emergency syncope care by reducing low-yield admissions and identifying patients who are unsafe for discharge from the ED. This study, entitled PACES: Practical Approaches to Care in Emergency Syncope, will help increase the quality and value of emergency care, and advance the field of syncope research.